I mentioned vodka and vinegar as problematic carbon sources in the previous posts, not biopellets, but since you bring it up...
I am reserving judgement on biopellets until more people report back with long term success stories, or until we see some more science supporting this new technology. While many claim short term successes with biopellets, I'm hearing more and more about coral necrosis with long term use. Possible causes could be too little N and P, leading to coral starvation (which could then be remedied by supplemental nutrition...(put another way: not much survives in a desert). It could also be that the high bacterial load supported by the biopellets introduces nutritional oscillations when what corals need is stability. Those are just two possibilities that could conceivably lead to problems. I don't claim either hypothesis as true. But until the biopellet bandwagon has some more science in its gas tank, I'll advise proceed with caution. That said, I'll be happy to jump on board when the biopellet recipe for long term reef stability has been figured out. My hope is that this new technique revolutionizes reef husbandry. But for now I'm raising coral, not guinea pigs.